Cleaning iron or steel



March 19, 1935.

CLEANING IRON OR STEEL Filed June 4, 1931 leo/v Cerf/bof'.

UIN

Hor tf1/H7156 INVENTOR.

v A TTORNE Y.

H. scHAGRlN 1,995,192

Paternal Mar. 19, 1935 Y UNITEzoL` STATES PATENT OFFICE my ssamm, oak .Park, nl., assigner, by

mesne assignments, to Robert laxalm. Application-June 4, 1931, serial No. 542,001

Claims.

This invention relates to a process for cleaningr iron or steel, and particularly for the removal of 'scale formed during annealingor hardening. In the manufacture of hardened steel parts, it is 6 customary to have the steel'in a soft condition during processing, and thereafter harden vthe steel in a suitable furnace and grind or polish the steel 'to-Inalform., Also, it is'customary to anneal` cast iron to form soft iron. In the commercial lo tmanufacture. of such parts, a hard scale is usuvally formed in the furnace, and. if not removed prior to grinding or polishing, would result in the serious wear of such grinding equipment. While numerous processes purport to remove scale, it has been found that such processes either appreciably etch the iron'or steel during the removal of the. scale or fail to completely removethe scale, lparticularly in inaccessible places caused by the drilling ofrecesses, and the like. I An object of this invention is to devise a simple, economical and speedy process for the removal of scale in such manner as'to avoid the above objections.

The drawing isia diagrammatic ,showing illustrative of. the steps in the process.

As actually applied, iron or steel covered with scale is made the cathode in a sulphuric acid solution. This solution has preferably between 10 and per cent acid, and contains as an anode a material likelead, which is substantially insoluble' inthe electrolyte. The temperature ofthe bathvis maintained between 110 and 120 degrees ,steel in connection with the'preparation of hard.

Fahrenheitpreferably 120 degrees Fahrenheit-, while the current density is maintained at between and 60 amperes per square foot of cath-- ode. It has b'een found that the average vscale is completely removed in from 6 to 12 minutes.

The iron or steel is removed from the bath, and in this condition has a dark-coloredappearance. It is washed in water to remove the acid, and is then made the anode in a bath for brightening the surface. This -bath is preferably alkaline and comprises about 2 to 8 ounces of sodium hydroxide or other alkali, and between Zand 4 ounces of trisodium phosphate per gallon of water. The trisodium phosphate may be omitted, if desired, but better results are secured with it. The cathode is preferably o f iron, although any other insoluble material, such as' lead, may be used. TheA 50 current density in this bath isimmaterial, since no electrolytic action isa-desired. The temperature of this bath is between 180`degrees` Fahrenheit and 200 degrees Fahrenheit. It has been found that the dark colorof the iron or steel is changed in a 'few seconds to 'a bright rust-resist-y ing surface, which may be ground or polished with ease. The cleaned part is then dipped into hot water, which .removes most of the caustic from the steel surface and leaves the surfacedry after a brief exposure in the air.

Whilel some departure from the conditions of temperature, current density and strength of solutions is permissible, it has been found that the best results are obtained in accordance with the above disclosure. In practice, the first bath has l0v acid added thereto at regular intervals to compenl sate for the loss of acid and maintain the strength of solution. After awhile, the amount of iron in the solution becomesjso great that itis advisable to throw out the entire solution and start anew. 151

' I'he solution in the third bathis not appreciably affected by use and need only be, fresheriedatl intervals vto clean the solution from suspended iron particles. i

This process has been successfully `applied-to 20 both iron and steel. As practiced, it results in substantially no etching and leaves a surface clean enough even for immediate soldering. It is important that the cleanedl article be taken out of the first bath promptly upon the removal of 25 the scale. While short 'periods of time in excess of thatrequired for scale removal will not causev any appreciable etching, prolonged stays in the n first bath will result in damage.

I claim: 3 '1'. A process of removing scale from iron or ened machine parts having scaly surfaces as the result of such hardening and which surfaces are 35 to be prepared for trueing operations while preventing lwdrogen embrittlement and pitting -peres per squarefoot 'of cathode area for a periodwithin the limits of said trueing operations which comprises making such ironor steel the cathode in ten to fifteen per cent sulphuric acid, maintain- 40 ing the temperature of said acid at to 120 degrees Fahrenheit/providing an anode of substantially insoluble material, and maintaining a current density of between fifty and sixty amnot in excess of about 1 2 minutes.

2. The process of claim l, in which the cleaned article is brightened by thereafter making it the anode in a solution containing sodium hydroxide and trisodium phosphate at a temperature tween and 200 degrees Fahrenheit.

3. The process of claim 1,' in which the cleaned article is brightened by thereafter making it the anode in a bath containing between two and eight ounces of sodium hydroxide per gallon of be' so.

' two and four ounces of trisodium phosphate per.

t Fahrenheit.

4. The process of claim 1, in which the cleaned article Ais brightened by thereafter making it the anode in a solution containing between two. and eight ounces of sodum hydroxide and between gallon of water, while mantaining the temperature between 180 and 200 degrees Fahrenheit.

5. The process of removing scale from iron or `steel in connection with the preparation of hardened machine parts having sealy surfaces as the result of such hardening and which surfaces are to be prepared for trueing operations while preventing' hydrogen embrittlement y and pitting within the limits of said trueing operations, which comprises making said 'article the cathode in a bain or ten to uiteen per cent mipnuric acm,

' sity of between fty and sixty amperes per square foot of cathode area, with an anode of substarl.

tially insoluble material for a period not in excess of about 12 minutes, withdrawing said article from this bath after the removal of the scale, then making said article the anode in a bath co'ntaning about'four ounces pf sodium hydroxide and between two and four ounces of trisodium phosphate per gallon of water; maintained between 180 and 200 degrees Fahrenheit, keeping said article in this `bath until the dark surface is brightened, and then removing said article fromsaid bath and dipping it into hot water to remove a vporion oi.' the caustic soda..V v v HARRY vscrriiGR1N/.- 

